JP4167326B2 - Aluminum alloy automatic transmission spool valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spool valve for an automatic transmission made of an aluminum alloy having excellent dimensional accuracy and wear resistance and seizure resistance.
[0002]
[Prior art and problems to be solved by the invention]
Low-carbon steel, low-carbon alloy steel case-hardened steel, and JIS structural alloy with emphasis on machinability as sliding members used in devices that require a leak-free seal, such as conventional hydraulic actuators Free-cutting steel such as steel SUM24L is used, and after blank cutting (header etc., depending on the shape, combined processing of plastic processing and cutting), carburizing and quenching is given to provide wear resistance, Polished to finish. However, since the steel spool valve has a large specific gravity, its operation response is poor.
[0003]
Recently, for the purpose of reducing the weight of automobiles and the like, hydraulic actuators tend to be cast aluminum alloys, and sliding members used for them are made of aluminum alloys. As the aluminum alloy, mainly A6061 system or quenched by water cooling after 2 hours solution treatment at T ₈ treated material (520 ° C. of A6000 system of the free-cutting material such as, cold working, and then at 170 to 180 ° C. A material subjected to an artificial age hardening treatment for 8 hours is used. After these aluminum alloys are cut, they are polished to the required accuracy, then hard anodized, and finally finished by polishing. Depending on the shape, as in the case of headers, etc., plastic processing is applied to A6000 series O material, blanking is performed by cutting, T ₆ or T ₇ treatment is performed, and then the steps following polishing are performed as described above. Is going. A6000 series aluminum alloy is suitable for a spool material because it has good plastic workability such as forging and can be hard anodized.
[0004]
In the case of a spool valve, the cost of using steel as a material is lower than that of an aluminum alloy. However, since the main body that receives the spool valve is made of cast aluminum, the difference in thermal expansion between the main body and the spool valve is large. When the temperature is increased during use, there is a problem that a large gap is generated between the inner wall of the hole of the main body and the outer surface of the spool valve, and the leakage of hydraulic oil increases.
[0005]
On the other hand, the aluminum alloy spool valve has less hydraulic oil leakage and good response, but has a problem that it is more expensive than the steel spool valve. Therefore, aluminum alloy spool valves are mainly used for automatic transmissions for high-end automobiles, and steel spool valves are frequently used for mass-class automobiles.
[0006]
When manufacturing a spool valve by cutting a material that does not contain free-cutting components of A6000 series aluminum alloy, chips are connected during processing, cutting performance is poor, and chips are bitten to reduce dimensional accuracy. In addition, it is necessary to frequently remove chips. In addition, since the work material is usually an extruded material of A6000 series aluminum alloy, the material itself has a residual stress, and bending, waviness and the like occur after cutting. Furthermore, since cutting workability is poor, bending, waviness, etc. are promoted by stress during processing.
[0007]
In order to solve the problem of low machinability, it is conceivable to use a so-called free-cutting material to which a free-cutting element such as lead is added as an aluminum alloy material, but the free-cutting material is generally only expensive. There is also a possibility that lead etc. may cause pollution. If the free-cutting steel was also subjected to normal T ₈ processing, the residual stress of the material itself, there are the same bend, causing such undulation. Therefore, there is a demand for a technique that can be easily cut without using a free-cutting material and that can manufacture a sliding member such as a highly accurate and highly coaxial spool valve at a low cost.
[0008]
On the other hand, various surface treatments have been proposed to reduce the friction of the sliding member, but the most common is hard anodizing treatment. For example, Japanese Patent Laid-Open No. 5-44865 discloses a method for manufacturing an aluminum valve spool, in which a corner portion of a base material is formed into an arc shape and a 5 to 25 μm anodic oxide film is uniformly formed on the surface of the base material. Disclosure. However, the hard anodizing treatment itself is expensive, and the anodized film has insufficient wear resistance, and the fine powder and dust of the worn anodized film are caught in the sliding surface, resulting in high local pressure. There is also a problem of causing scratches and burn-in. As described above, the anodized film is formed to prevent seizure between aluminum and to improve the wear resistance, but the actual situation is that the purpose is not sufficiently achieved.
[0009]
Further, even when the hard anodizing treatment is performed, it is necessary to perform a polishing process in order to obtain dimensional accuracy before that. In addition, in the case of the hard anodizing treatment, the current density varies depending on the location of the substrate surface, so that the film thickness is not uniform and it is necessary to perform polishing again after the treatment. Thus, in the case of the hard anodizing treatment, there is a problem that not only sufficient wear resistance and seizure resistance cannot be obtained, but also the process is complicated and the production cost is increased.
[0010]
Therefore, the object of the present invention is that it can be easily cut without using a free-cutting material, and has excellent wear resistance and seizure resistance that cannot be obtained by hard anodizing treatment, and To provide a spool valve for an automatic transmission made of an aluminum alloy having good dimensional accuracy.
[0011]
[Means for Solving the Problems]
As a result of diligent research in view of the above problems, the present inventors have made the base material of the spool valve made of an aluminum alloy with no free-cutting component added, over-aged it, and coated and baked with a solid lubricant. By forming a solid lubricating film, (1) cutting becomes easy, and (2) residual stress is removed by overaging treatment, so that bending or undulation due to stress relaxation does not occur in the subsequent seizure process, As a result, the dimensional accuracy by cutting was improved, and (3) the solid lubricating film was found to provide better wear resistance and seizure resistance than the anodized film, and the present invention was completed.
[0012]
That is, the spool valve for an aluminum alloy automatic transmission according to the present invention comprises a base material made of an aluminum alloy and a solid lubricating film formed on the surface thereof, and the linear expansion coefficient of the base material is substantially constant in the operating temperature range. And the substrate has a dimensional accuracy of 5 μm or less. Since it does not contain a free-cutting component, cost reduction can be achieved, and a substantially constant linear expansion coefficient and dimensional accuracy of 5 μm or less can be achieved by overaging. In particular, the dimensional accuracy of 5 μm or less is a level that cannot be achieved by the T ₈ treatment / hard anodizing treatment.
[0013]
The solid lubricant film is at least one solid lubricant powder selected from the group consisting of fluororesin, molybdenum disulfide and graphite, and at least one selected from the group consisting of polyamideimide, polyimide, epoxy resin and phenol resin. The binder resin is preferably composed of fluororesin powder, molybdenum disulfide powder and polyamideimide. In addition, aluminum alloy base materials such as A6000 series have a hardness of 85 Hv or more due to overaging. A hardness of 85Hv or higher is a necessary level that has been confirmed on actual machines, and can be achieved only by overaging.
[0014]
The spool valve for an automatic transmission made of an aluminum alloy according to the present invention comprises (a) an overaging treatment of a base material made of an aluminum alloy that does not contain a free-cutting component, (b) machined into a predetermined shape, and then (c) It can be manufactured by coating a solid lubricant on the surface of the substrate and baking to form a solid lubricating film, and the temperature of the overaging treatment is preferably substantially the baking temperature or higher. . Since the machinability is improved by overaging, the cutting resistance is small during cutting, and the bending stress that presses the tool blade against the work material is reduced. In addition, since the residual stress of the material itself is small, cutting accuracy (coaxiality) is improved. Furthermore, since the temperature of the overaging treatment is substantially set to the baking temperature or higher, deformation such as bending due to the release of residual stress during baking can be prevented.
[0015]
The conditions for the overaging treatment are preferably 200 ° C. or more and 20 minutes to 2 hours, and the solid lubricant film baking conditions are preferably 200 ° C. or more and 10 minutes or more. Moreover, it is preferable to perform the solution treatment before the overaging treatment. Baking conditions of 200 ° C. or higher are particularly suitable when polyamideimide is used as a binder resin for a solid lubricant. In order to achieve a hardness of 85 Hv or more, the total time of overaging + baking is preferably 35 to 140 minutes.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
[1] spool valve
(A) The aluminum alloy used for the base spool valve base is an aluminum alloy with no free-cutting component such as lead, and particularly preferably an A6000 series aluminum alloy such as the A6061 series. The composition of A6000 series aluminum alloy is specified by JIS.
[0017]
(B) Solid Lubricant Film The solid lubricant composition used in the present invention comprises at least one solid lubricant powder selected from the group consisting of fluororesin, molybdenum disulfide and graphite, polyamideimide, polyimide, and epoxy resin. And at least one binder resin selected from the group consisting of phenol resins. Among these, a composition composed of fluororesin powder, molybdenum disulfide powder and polyamideimide is preferable.
[0018]
The thickness of the solid lubricating film is preferably 3 to 50 μm. When the thickness of the solid lubricating film is less than 3 μm, the durability of the solid lubricating film is insufficient. Further, even when the thickness is 50 μm, no further improvement in wear resistance and seizure resistance can be obtained. A more preferred thickness is 5 to 25 μm.
[0019]
[2] Spool valve manufacturing method
(A) Solution Treatment It is preferable to perform solution treatment before overaging the substrate made of aluminum alloy. The solution treatment condition is to heat and hold at 500 to 550 ° C. for 1 to 3 hours, whereby the alloy components are sufficiently dissolved. After heating and holding, quench by water cooling.
[0020]
(B) Since the base material may be slightly bent and deformed by waviness or the like due to the cold working solution treatment, it is bent and corrected by a straightening roll machine to ensure dimensional accuracy.
[0021]
(C) Dimensional accuracy such as concentricity is extremely important for an overaged spool valve, but it is extremely difficult to obtain the desired concentricity only by cutting because of the cutting resistance and the residual stress of the material itself. Met. The inventor has discovered that an overaging treatment may be performed on an aluminum alloy base material in order to ensure good machinability and dimensional accuracy. The solid lubricant is baked after the overaging treatment, but if the internal stress remains at that time, it will be released by heating and cause bending, undulation, etc., so the residual stress is sufficiently removed by overaging treatment. I have to keep it. In particular, the A6000-based standard T8 treated material has a large amount of residual stress in the linear direction, and is likely to bend and swell in the subsequent baking process. Accordingly, it is preferable that the overaging temperature is substantially equal to or higher than the baking temperature of the solid lubricant. Moreover, it is preferable that the total time of overaging + baking is within a range in which a hardness of 85 Hv or more can be secured. For this purpose, it is generally preferable to set the total time of overaging and baking to 35 to 140 minutes. Specific conditions for the overaging treatment are preferably 200 ° C. or more and 20 minutes to 2 hours, and more preferably 200 to 250 ° C. for 20 to 100 minutes.
[0022]
(D) Cutting process Cutting is performed to make the substrate over-aged into the shape of a spool valve. Since the overaged base material showed good machinability, not only the cutting efficiency is good, but also the cutting resistance during cutting is small, and the bending stress that presses the tool blade against the work material becomes small. In addition, since the residual stress of the material itself is small, cutting accuracy (coaxiality) is improved. As a result, the over-aged aluminum alloy substrate itself has not only excellent dimensional accuracy, but also excellent dimensional accuracy is maintained after baking of the solid lubricant film. Moreover, since sufficient dimensional accuracy can be obtained with the cutting process, an expensive polishing process can be omitted.
[0023]
(E) Coating and baking of solid lubricant The surface of the substrate is coated with a solid lubricant having the above composition. The binder resin in the solid lubricant is usually liquid or powder. In the case of a liquid binder resin, (1) a liquid binder resin is used such as an epoxy resin, or (2) it is liquefied by dissolving in an organic solvent such as polyamideimide or polyimide. In the case of a powdered binder resin, the binder resin is finely mixed with the solid lubricant powder. In the case of a liquid paint, it is applied to the surface of the substrate by dipping or spraying, and in the case of a powder, it is applied to the surface of the substrate by a powder coating method.
[0024]
The solid lubricant coating is baked at a temperature equal to or higher than the melting temperature or curing temperature of the binder resin. For example, in the case of polyamideimide, it is necessary to bake at a temperature of 180 ° C. or higher, preferably 200 to 250 ° C. The baking time depends on the temperature, but is preferably 10 minutes or more, and about 20 to 30 minutes is sufficient.
[0025]
Since the aluminum alloy base material is heated again by baking of the solid lubricant, it is released when there is residual stress. As a result, bending, undulation or the like may occur due to baking. This is a problem of the prior art, but according to the present invention, since the base material is pre-aged in advance, there is no possibility of bending, undulation or the like caused by baking of the solid lubricant.
[0026]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
[0027]
Reference example 1
After extruding a 14mm diameter extruded rod made of aluminum alloy (JIS A6061) at 520 ° C for 2 hours, solution treatment (quenching with water cooling), and then removing deformation such as bending and undulation with a straightening roll Sample No. 1 was prepared by over-aging at 240 ° C. for 1 hour. Also after the same solution treatment and straightening the same extruded bar, for 8 hours aging at 180 ° C. (T ₈ treated) to prepare a sample No. 2.
[0028]
Each sample was cut into a spool valve shape shown in FIG. 1, and the coaxiality was measured by the method shown in FIG. That is, two points A and B of the sample were supported, the end C was shaken, and the coaxiality was measured. FIG. 3 shows the variation of the coaxiality of each test piece No. 1 to 5 in Sample Nos. 1 and 2. As apparent from FIG. 3, sample No. 1 was over-aging treatment as compared to T ₈ treatment material (Sample No. 2), dimensional accuracy, represented by the concentricity is turned about two times better.
[0029]
The relative overaging material (Sample No. 1) and T ₈ treatment material (Sample No. 2), respectively the residual stress, Young's modulus, elongation and tensile strength were measured. The results are shown in FIGS. These results, in comparison to the over-aging treatment material (Sample No. 1) is T ₈ treatment material (Sample No. 2), the residual stress is 1/2 or less (see FIG. 4), the Young's modulus slightly It is large (see FIG. 5), the elongation is 1/2 or less (see FIG. 6), and the tensile strength is slightly reduced (see FIG. 7). As a result, it can be seen that the machinability is remarkably improved. Since the overaged material (Sample No. 1) has good machinability in this way, the cutting resistance during cutting is small, the bending stress that presses the tool blade against the work material is small, and the material itself It is considered that the cutting accuracy (coaxiality) is improved because the residual stress is small.
[0030]
Reference example 2
A solid lubricant composition was prepared from fine powder of polytetrafluoroethylene (PTFE), fine powder of molybdenum disulfide, and polyamideimide (degree of polymerization: 92%), and coated on the surface of an aluminum plate. Bake for 20 minutes at each temperature in the range of ° C. FIG. 8 shows the relationship between the degree of polymerization of polyamideimide in the obtained solid lubricating film and the baking temperature. As is apparent from FIG. 8, when the baking temperature reaches 240 ° C., the degree of polymerization of polyamideimide becomes almost 100%. As a result, it is found that the baking temperature of the solid lubricating film is preferably 240 ° C. or higher.
[0031]
Reference example 3
The same extruded rod of aluminum alloy as in Reference Example 1 was heat-treated at 240 ° C. FIG. 9 shows the relationship between the heat treatment time and the hardness of the heat-treated bar. As apparent from FIG. 9, in the case of the heat treatment at 240 ° C., a hardness of 85 Hv or more was obtained in about 40 to 120 minutes, but the hardness decreased below or above. Here, the hardness of 85Hv is a condition for satisfying the durability, and it has been confirmed by an actual machine. Since the heat treatment time at 240 ° C. is equal to the sum of the heating time for overaging and baking, for example, when the baking time is 20 minutes, in this example, the overaging time is 20 to 100 minutes.
[0032]
Reference example 4
In the same manner as in Reference Example 1, a cylindrical rod of aluminum alloy (A6061) was subjected to a solution treatment (quenching by water cooling) and then corrected, followed by an overaging treatment at 240 ° C. for 1 hour, and sample No. 3 ( A6061-overaging material) was produced. Also after the same solution treatment and straightening the same cylindrical rod, for 8 hours aging at 180 ° C. (T ₈ process), sample No. 4 the (A6061-T ₈ material -1) Produced. The outer diameter of each sample was 12.000 mm at 120 ° C.
[0033]
Each sample was embedded with a sheath type thermocouple, heated to 150 ° C. in a furnace, and the change in outer diameter at the time of temperature reduction was measured with a heat-resistant micrometer. When the measured value of the outer diameter at each temperature is X mm, the linear expansion coefficient is expressed by (X / 12) × 100%. FIG. 10 shows the relationship between the linear expansion coefficient thus obtained and the temperature. From Figure 10, T ₈ treatment material (Sample No. 4) linear expansion coefficient at a temperature of about 60 ± 20 ° C. has been found to be lower. On the other hand, since the linear expansion coefficient of the overaged material (sample No. 3) changes substantially linearly in the temperature range of about 30 ° C. to 120 ° C., the linear expansion coefficient is substantially constant. I understand that.
[0034]
Example 1, Comparative Examples 1 and 2
The same overaged material (Sample No. 1) as in Reference Example 1 is cut into the spool valve shape shown in Fig. 11, coated with a solid lubricant composition of the same composition as in Reference Example 2, and baked at 240 ° C for 20 minutes. A spool valve of Example 1 was produced.
[0035]
The same T ₈ treated material (sample No. 2) as in Reference Example 1 was cut into a spool valve shape shown in FIG. 11 and subjected to hard anodizing treatment to produce a spool valve of Comparative Example 1. In addition, steel rods with a diameter of 14 mm (JIS SCR420) were carburized in a propane gas-modified carburizing atmosphere gas at 930 ° C and then quenched by oil cooling from 870 ° C. Was made.
[0036]
Each spool valve was installed in an aluminum housing jig, and the ring gap leakage amount at an oil temperature of 35 to 120 ° C. was measured. The results are shown in FIG. As is clear from FIG. 12, in the case of the carburized / quenched steel spool valve of Comparative Example 2, the difference in the linear expansion coefficient between steel and aluminum was originally large. Increased. The T ₈ treatment - if hard anodized spool valve (Comparative Example 1), the total oil temperature range of thirty-five to one hundred and twenty ° C., the leakage amount of the overaging - Solid lubricant film spool valve (Example 1) significantly more than, At 80 ° C. or less, the amount was higher than that of the carburized steel spool valve (Comparative Example 2). Since the leakage amount is directly connected to the hydraulic oil pump load, when the leakage amount increases, not only the energy loss increases but also the responsiveness of the spool valve decreases.
[0037]
Examples 2 and 3 and Comparative Examples 3 to 6
A spool valve having the shape shown in FIG. 1 and a spool valve having the shape shown in FIG. 11 were produced under the same conditions as in Example 1 and Comparative Examples 1 and 2. Each spool valve is as follows.
Example 2: A6061-over-aged / solid lubricant film Comparative example of spool valve with the shape shown in FIG. 1: A6061-T ₈ treatment / anodized film Comparative example of spool valve with the shape shown in FIG. 1: Carburizing and quenching of steel spool valve embodiment having the shape shown in Figure 1 3: A6061- overaging, solid lubricant films view of a shape shown in 11 spool valve Comparative example 5: spool valve comparison of the shape shown in A6061-T ₈ processing and anodized film 11 Example 6: Steel carburizing and quenching Spool valve with the shape shown in FIG.
Each spool valve was installed in an aluminum housing jig, and the response time at an oil temperature of 20 to 120 ° C. was measured. The results are shown in FIG. As is apparent from FIG. 13, in the case of the small and thin spool valve having the shape of FIG. 11, the difference in weight between the spool valve of Example 3 and the spool valves of Comparative Examples 5 and 6 is not so large, so that remarkable responsiveness is achieved. In the case of the shape of FIG. 1, the spool valve made of the overaged / solid lubricating film A6061 of Example 2 is more than the carburized and quenched steel spool valve of Comparative Example 4. It was very responsive and was better in the entire measured temperature range than the A6061 spool valve treated with T ₈ and anodized in Comparative Example 3.
[0039]
Example 4 and Comparative Examples 7 to 13
In the wear test and dynamic friction test using a chip-on-disk, the disk side was made of an ADC equivalent material, and the following substrate was subjected to the following surface treatment as a chip.
Example 4: A solid lubricating film (PTFE + MoS ₂ + polyimide) on a G67 substrate.
Comparative Example 7: G67 Hard anodized film with a thickness of 20 μm on the base material.
Comparative Example 8: G67 substrate with Ni-P ₁₀ plating.
Comparative Example 9: ASCM16 (no surface treatment).
Comparative Example 10: H-38 (no surface treatment).
Comparative Example 11: A4032 (no surface treatment).
Comparative Example 12: G67 Chip with T ₈ treatment on substrate (no surface treatment).
Comparative Example 13: A6061 Chip with T ₆ treatment on substrate (no surface treatment).
[0040]
The test conditions were as follows.
(1) High surface pressure wear test Surface pressure: 3MPa
Disk rotation speed: 12.5 m / s
Test time: 30 minutes Sliding distance: 22,500m
ATF oil drop rate: 16 ml / min
[0041]
(2) Low surface pressure wear test Surface pressure: 0.1 MPa
Disk rotation speed: 6.2 m / s
Test time: 120 minutes Sliding distance: 44,600m
ATF oil drop rate: 16 ml / min
[0042]
(3) Dynamic friction test surface pressure: 0.1 to 5 MPa
Disk rotation speed: 25.5 m / s
ATF oil drop rate: 16 ml / min
[0043]
The wear test results are shown in FIGS. 14 and 15, respectively, and the dynamic friction test results are shown in FIG. 14 and 15, it can be seen that the tip of Example 4 having a solid lubricating film has significantly less wear than the tips of Comparative Examples 7-11. Also, from FIG. 16, the tip of Example 4 having a solid lubricating film has a wider surface pressure range than the tip of Comparative Example 7 having a hard anodized film and the tips of Comparative Examples 11 to 13 having no surface treatment. It can be seen that the coefficient of dynamic friction is small. In Comparative Examples 7 and 11 to 13, baking occurred, and the test of FIG.
[0044]
【The invention's effect】
As described above, the spool valve of the present invention is not only having excellent wear resistance and seizure resistance, but also having an excellent wear resistance and seizure resistance since it is coated with a solid lubricant after being over-aged to an aluminum alloy base material. Since the residual stress is almost removed by aging, the machinability is good and it has excellent dimensional accuracy (coaxiality) of 5 μm or less without expensive polishing. Therefore, when used as a spool valve or the like, the amount of leakage can be significantly reduced.
[0045]
Moreover, since the machinability is improved by overaging, the aluminum alloy does not need to contain a free-cutting component, and therefore the cost of the spool valve can be reduced. For example, in the case of a spool valve, the cost can be reduced by about 30% compared to a steel spool valve. In addition, since it does not contain lead or other free-cutting components, it contributes to pollution prevention.
[0046]
The spool valve of the present invention having the above characteristics is suitable as a spool valve used for an automatic transmission for a high-class automobile or the like.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a spool valve.
FIG. 2 is a schematic view showing a method for measuring the coaxiality of a spool valve.
FIG. 3 is a graph comparing the variation in coaxiality for each test piece for an over-aged aluminum alloy (sample No. 1) and a T ₈ treated aluminum alloy (sample No. 2).
[4] The overaging aluminum alloy (Sample No. 1) and T ₈ treated aluminum alloy (Sample No. 2), it is a graph comparing the residual stress.
[5] The overaging aluminum alloy (Sample No. 1) and T ₈ treated aluminum alloy (Sample No. 2), it is a graph comparing the Young's modulus.
[6] The overaging aluminum alloy (Sample No. 1) and T ₈ treated aluminum alloy (Sample No. 2), which is a graph comparing elongation.
FIG. 7 is a graph comparing the tensile strength of an over-aged aluminum alloy (sample No. 1) and a T ₈ treated aluminum alloy (sample No. 2).
FIG. 8 is a graph showing the relationship between the degree of polymerization of polyamideimide in a solid lubricant and the baking temperature.
FIG. 9 is a graph showing the relationship between heat treatment time and hardness of an aluminum alloy.
FIG. 10 is a graph showing the relationship between linear expansion coefficient and temperature for an over-aged aluminum alloy (sample No. 3) and a T ₈ treated aluminum alloy (sample No. 4).
FIG. 11 is a schematic cross-sectional view showing another example of a spool valve.
FIG. 12 shows an overaged / solid lubricant film spool valve (Example 1), a T ₈ treated / hard anodized film spool valve (Comparative Example 1), and a carburized / hardened steel spool valve (Comparative Example 2). It is a graph which shows the relationship between an annular | circular gap clearance amount and oil temperature.
[13] overaging-solid lubricating film spool valve (Example 2,3), T ₈ processing and hard anodic oxide film spool valve (Comparative Example 3, 5), and carburizing and quenching of iron or steel spool valve (Comparative Example 4 and 6) are graphs showing the relationship between response time and oil temperature when various shapes are employed.
FIG. 14 is a graph showing the relationship between the dynamic friction coefficient at high surface pressure and the amount of wear for various chips.
FIG. 15 is a graph showing the relationship between the dynamic friction coefficient and the wear amount at low surface pressure for various chips.
FIG. 16 is a graph showing the relationship between surface pressure and dynamic friction coefficient for various chips.

Claims (1)

A spool valve for an automatic transmission in which a solid lubricating film is formed on a surface of a base material made of an aluminum alloy, wherein the base material is overaged, and the solid lubricating film is solid on the surface of the base material A spool valve for an automatic transmission , which is formed by coating and baking a lubricant, and the temperature of the overaging treatment is equal to or higher than the baking temperature .

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